1. Field of the Invention
This invention generally relates to a pointing device and receiving unit, and more particularly, to a pointing device and receiving unit that utilize an Ultra Wide Band (hereinafter simply referred to as UWB) signal.
2. Description of the Related Art
FIG. 1 shows a conventional coordinate input device. With reference to FIG. 1, the coordinate input device includes a pointing device 910 and a receiving unit 920. The pointing device 910 is operated by users. The receiving unit 920 receives information transmitted from the pointing device 910. The pointing device 910 and the receiving unit 920 send and receive data by wireless with frequencies of several gigahertz.
The pointing device 910 is a mouse or a pen-type coordinate input device, for example. The pointing device 910 includes an antenna 911, an RF unit 912, a control unit 913, a switch unit 914, a sensor unit 915, and a power unit 916. The power unit 916 includes a dry battery or the like so as to provide each unit with electricity. The switch unit 914 is an input device such as a click button, a wheel button, or the like. The sensor unit 915 is a ball-type or optical input device for inputting an amount of movement. Information on an operation is inputted into the switch unit 914 and information on the amount of movement is inputted into the sensor unit 915. Those inputted pieces of information are inputted into the control unit 913. Particularly, the information on the amount of movement inputted from the sensor unit 915 is inputted into a coordinate detection unit 913a, which is included in the control unit 913. The information on the amount of movement is composed of analog signals. The coordinate detection unit 913a calculates information on X-coordinate and Y-coordinate with the inputted analog signals. After the information on the operation and the information on the coordinates are processed in the control unit 913 in a certain manner, the information on the operation and the information on the coordinates are inputted into the RF unit 912 as a data signal. In the RF unit 912, the inputted data signal is converted into a frequency signal, and the frequency signal is transmitted from the antenna 911.
The receiving unit 920 includes an antenna 921, an RF unit 922, a control unit 923, and an interface unit 924. The frequency signal received by the antenna 921 is inputted into the RF unit 921, and is converted into a data signal. After the data signal is inputted into the control unit 923, the data signal is outputted into a personal computer or the like from the interface control unit 924. The interface unit 924 is a USB (Universal Serial Bus), a PS/2 mouse, an IEEE1394 interface component, or the like.
However, in the above-mentioned architecture, the sensor unit 915 includes a ball-type or an optical unit. Therefore, there is the problem in that the pointing device 910 becomes heavy, and the user-friendliness is degraded. In the case where the optical unit is employed, there is the problem in that the power consumption is increased and the dry battery having a larger capacity is required in the power unit 916 in order to supply more electricity. This problem results in an increase in weight of the entire pointing device 910.
Under the circumstances, some coordinate input devices have been proposed. The proposed coordinate input devices do not require the above-mentioned sensor unit 915. For example, Japanese Laid-Open Patent Application Publication No. 9-218742 discloses a pen-type coordinate input device that detects coordinates of the pen tip position with the use of electric waves. More specifically, the above-mentioned pen-type coordinate input device is equipped with an antenna in the close vicinity of the pen tip. The electric waves transmitted from this antenna are received by two antennas installed in an information processing unit. With the use of signals received by those two antennas, the information processing unit specifies the coordinate position of the transmitting antenna in the close vicinity of the pen tip, based on the principle of triangular surveying.
Japanese Laid-Open Patent Application Publication No. 7-5979 discloses a coordinate input device that detects the coordinates of the pen tip position with the use of laser beams. More specifically, a reflector such as aluminum tape or the like is attached to the tip of an ordinary writing material such as a pen, a ballpoint pen, or the like. With the use of the laser beams, the coordinate input device scans the reflector from two directions. The coordinate input device detects the coordinates of the pen tip position based on angles of two beam paths when the reflector is detected.
However, the above-mentioned coordinate input device disclosed in Japanese Laid-Open Patent Application Publication No. 9-218742 requires two different transmission systems: one transmission system for transmitting the information on operation and the other transmission system for transmitting the information on coordinates. Therefore, there is the problem in that the power consumption is increased. Consequently, a battery having a large capacity needs to be mounted on the pen-type coordinate input device. As a result, the increased weight lowers the user-friendliness.
The above-mentioned coordinate input device disclosed in Japanese Laid-Open Patent Application Publication No. 7-5979 requires a mirror or the like in order to scan or detect laser sources and laser beam paths. As a result, the entire system becomes complicated and larger in size.